Lidocaine sensitizes the cytotoxicity of 5-fluorouacil in melanoma cells via upregulation of microRNA-493.

Lidocaine is a well-documented local anesthetic that has been reported to sensitize the cytotoxicity of cisplatin in cancer cells. However, little information is available concerning whether lidocaine sensitizes the cytotoxicity of 5-fluorouracil (5-FU) in melanoma cells. The study was aimed to explore the effects and mechanisms of lidocaine on the sensitivity to 5-FU in the melanoma cell line SK-MEL-2. Cell viability and apoptosis were analyzed after administration of different concentrations of lidocaine, 5-FU, or the combinations. Expression of microRNA (miR)-493 was assessed following lidocaine administration. The target genes of miR-493 were verified by luciferase reporter assay, PCR, and Western blot. The effects of abnormal expression of miR-493 and/or SRY-Box 4 (SOX4) on cell viability, apoptosis, and key proteins in phosphatidylinositol-3-kinase (PI3K)/AKT and the Smad pathways were detected. The effects of (0-100 uM) lidocaine on cell viability and apoptosis was not obvious; however, lidocaine could significantly increase the cell viability and inhibit apoptosis in 5-FU-treated cells. In addition, lidocaine induced upregulation of miR-493 in a dose-dependent manner, and we confirmed that the effects of miR-493 on the sensitivity were by upregulating miR-493. Moreover, we verified that Sox4 was a target of miR-493, and Sox4 overexpression decreased the sensitivity to 5-FU. Besides, Sox4 overexpression increased the levels of p-PI3K, p-AKT, p-Smad2 and p-Smad3, and Sox4 suppression showed contrary results. Our results suggest that lidocaine sensitizes the cytotoxicity of 5-FU in melanoma cells via upregulation of miR-493, which might be involved in SOX4-mediated PI3K/AKT and Smad pathways.